The present invention relates to an improvement in the manufacture of tantalum solid electrolyte capacitors and is concerned more particularly with the step of the oxidation of the anodes. It is necessary to recall here the principal steps of manufacture of tantalum capacitors as described in the U.S. Pat. No. 3,166,693 to Haring and Taylor.
The anode is essentially produced from tantalum powder of well defined grain size by pressing followed by sintering at temperatures depending upon the performances of the capacitor to be obtained, these temperatures being in the neighbourhood of 1800.degree. C. By means of this metallurgical treatment, it is possible to obtain a porous anodic structure which is thereafter subjected to a surface anodic oxidation for the purpose of forming, over the whole of the surface of the anodic sponge, a layer of tantalum oxide which performs the function of the dielectric of the capacitor. The oxidized anodic structure is thereafter covered by a layer of manganese dioxide obtained by impregnating the porous structure with a manganese salt solution which is decomposable into dioxide by pyrolysis. The pyrolysis operation sometimes causes a deterioration in the oxide layer which must be subsequently reformed. In order to obtain a dioxide layer of sufficient thickness, it is also customary to proceed with a number of successive impregnations followed by pyrolyses and reformations. There then follows the formation of the cathode of the capacitor by deposition of one or more conductive layers upon the anodic structure thus obtained. The capacitor is finished by an encapsulating step.